Flame-retardant resin compositions

ABSTRACT

BIS(AR-HALO-AR-ALKENYLOXPHENYL) COMPOUNDS WHEREIN THE AROMATIC RINGS ARE LINKED BY A COVALENT BOND, A SULFUR OR OXYGEN ATOM, A SECONDARY OR TERTIARY AMINO GROUP, OR A DIVALENT ALIPHATIC GROUP; PROCESSES FOR PREPARING SUCH COMPOUNDS BY REACTING AN ALKENYL HALIDE WITH AN APPROPRIATE BIS(AR-HALO-AR-HYDROXPHENYL) COMPOUND OR WITH A SALT THEREOF; AND THE USE OF SUCH COMPOUNDS AS FLAMERETARDANT AGENTS FOR NORMALLY FLAMMABLE SYNTHETIC RESINS, ESPECIALLY FORMED SYNTHETIC RESINS.

United States Patent ABSTRACT OF THE DISCLOSURE Bis(ar-halo-ar-alkenyloxyphenyl) compounds wherein the aromatic rings are linked by a covalent bond, a sulfur or oxygen atom, a secondary or tertiary amino group, or a divalent aliphatic group; processes for preparing such compounds by reacting an alkenyl halide with an appropriate bis(ar-halo-ar-hydroxyphenyl) compound or with a saltthereof; and the use of such compounds as flameretardant agents for normally flammable synthetic resins, especially foamed synthetic resins.

BACKGROUND o THE INVENTION Field of the invention This invention relates to novel compounds having flame-retardant properties, to synthetic resin compositions containing these compounds, and especially to synthetic resin compositions containing a flame-retardant agent which does not have an unduly deleterious effect on the mechanical properties of foamed products prepared from the compositions.

Description of the prior art It is known that many synthetic resins, especially hydrocarbon resins such as polyethylene or polystyrene, have a tendency to burn in air and that this tendency is also noticeable when the resins are in an expanded form, e.g., foamed polystyrene. It has been proposed to reduce this tendency by adding a flame-retardant agent, e.g., certain halogen compounds, to impart flame-retardant properties to the resin. However, this proposal has not been entirely successful, since many compounds which would otherwise be good flame-retardant agents have a deleterious effect on the mechanical properties of the resin. For example, it has been found difficult to produce a satisfactory flame-retardant foamed polystyrene containing a halogen compound as a flame-retardant agent, because the mechanical properties of the polystyrene can be so adversely affected that there is a tendency for the foamed polystyrene to be distorted or to collapse.

An object of the invention is to provide novel compounds having flame-retardant properties.

Another object is to provide novel flame-retardant synthetic resin compositions.

A further object is to provide novel foamable synthetic resin compositions which, when foamed, have excellent flame-retardant and mechanical properties.

An additional object is to provide processes for preparing such novel compounds and compositions.

SUMMARY OF THE INVENTION These and other objects are attained by (l) reacting an alkenyl halide with a bis(ar-halo-ar-hydroxyphenyl) compound wherein the aromatic rings are linked by a covalent bond, a sulfur or oxygen atom, a secondary or tertiary amino group, or a divalent aliphatic group, or with a salt of such a compound, to form the corresponding bis(ar-halo-ar-alkenyloxyphenyl) compound and (2) incorporating the bis(ar-halo-ar-alkenyloxyphenyl) com- Patented Feb. 1, 1972 pound into a normally flammable synthetic resin composition as a flame-retardant agent.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following examples are given to illustrate the invention and are not intended as a limitation thereof. Unless otherwise specified, quantities mentioned are quantities by weight.

Example I.Prepare 2,2 bis (4-allyloxy-3,5-dibrornophenyl)propane by 1) stirring and boiling under reflux for 6 hours a mixture of 54 parts of 2,2-bis(4-hydroxy 3,5-dibromophenyl)propane, 60 parts of potassium carbonate, 28.72 parts of allyl bromide, 1 part of sodium iodide, and 80.8 parts of methyl ethyl ketone, (2) adding 500 parts of Water to separate an oil that gradually solidifies, (3) collecting 57 parts of an off-white solid having a melting point of 113-115 C., and (4) recrystallizing twice from acetic acid to yield 39.9 parts of white prisms having a melting point of 118-119 C.

Example II.--Tumble 100 parts of foamable polystyrene beads containing 6% of a pentane blowing agent for one minute with 0.5 part of a solution of 20% of sorbitan monolaurate in methylated spirits, and then tumble them for one minute with 0.5 part of powdered 2,2- bis(4-allyloxy-3,S-dibromophenyl)propane. Prefoam the resultant coated beads by exposing them to steam for four minutes at a pressure of 9 p.s.i.g., place the prefoamed beads in a suitable mold, and inject steam through small holes in the mold walls to expand the prefoamed beads to a foamed polystyrene block having a density of one pound per cubic foot.

The block of foamed polystyrene thus formed is pure white, has excellent mechanical properties, and is free from distortion.

Test the foamed product for flame-retardant properties by British Standard 3932 (1965), using six sample strips 8 inches x 1 inch x /2 inch cut from the molded block. The Flame Test Rating resulting from this test is 6 out of 6 self-extinguishing.

As demonstrated above, a foamed product having an excellent degree of flame-retardancy as Well as excellent mechanical properties and freedom from distortion is obtained when the foamable polystyrene beads from which it is prepared are coated with 2,2-bis(4-allyloxy-3,5-dibromophenyl)propane. Similar results are observed when:

l) The foamable beads are beads of polymethyl methacrylate, polyvinyl acetate, a styrene-acrylonitrile (:20) copolymer, a styrene-alpha-methylstyrene-acrylonitrile (80:5 :15) terpolymer, a styrene-methyl methacrylate (:10) copolymer, or a toughened polystyrene having a polybutadiene rubber content of 5% or (2) The flame-retardant agent is bis (2-allyloxy-3 ,5 -dibromophenyl) methane, 2,2-bis(2-allyloxy-3,5-dibromophenyl) propane,

bis (4-allyloxy-3,S-dibromophenyl) methane,

2,2-bis (4-allyloxy-5-bromophenyl) propane,

2,2-bis (4-allyloxy-3-bromo-5-chlorophenyl propane, bis(4-allyloxy-3,5-dibromophenyl) ether,

bis (4-allyloxy-3,S-dibromophenyl) sulfide, 4,4'-diallyloxy-3,3,5,5'-tetrabromodiphenylamine, or 4,4'-diallyloxy-3,3 ',5 ,5 '-tetrabromodiphenyl.

Example Ill-Charge 259 parts of water, 0.94 part of polyvinylpyrrolidone having a molecular weight of about 300,000, 0.25 part of sodium pyrophosphate, 0.02 part of sodium bicarbonate, parts of styrene, 0.2 part of 2,2-bis(4-al1yloxy-3,5 dibromophenyl)propane, 0.7 part of benzoyl peroxide, and 6.35 parts of petroleum ether having a boiling range of 4550 C. to an autoclave provided with a stirrer. Pressurize with nitrogen to a pressure slightly above atmospheric pressure, close the autoclave, and heat to 80 C. for 10 hours while stirring. At this stage about 50% of the styrene has polymerized. Now add 1.41 parts of the petroleum ether under pressure over a period of 3 hours, and continue the polymerization with stirring at 82 C. for a further 21 hours. Then allow the autoclave to cool, vent it to atmospheric pressure, open the autoclave, and recover the resultant polymer beads.

Prefoam the beads in a steam atmosphere for four minutes to form spherical foamed beads which are free from surface deformities and have a bulk density of 11 ounces per cubic foot. Allow the prefoamed beads to dry on an open tray for one day, and then mold them into a one foot cube block. The block has good physical properties, the beads being well bonded together.

Test the foamed product for flame-retardant properties as in Example 11. The Flame Test Rating is 6 out of 6 self-extinguishing.

Example IV.Spray both major surfaces of a foamed polystyrene sheet having a thickness of V2 inch and a density of about one pound per cubic foot with a 10% aqueous dispersion of 2,2-bis(4-allyloxy-3,5-dibromophenyl)propane, and dry the coated sheet. The coated sheet has good self-extinguishing properties as measured ing a thickness of about V2 inch and a density of two pounds per cubic foot.

Test the foamed product for flame-retardant properties as in Example'II. The resulting Flame Test Rating is 6 out of 6 self-extinguishing.

Example VI.-'Extrude foamable polystyrene pellets containing 1% of finely-divided silica, 1% of zinc stearate, 10% of butene, and 0.5 of 2,2-bis(4-allyloxy-3, -dibromophenyl)propane at a pressure of 500 p.s.i. and a temperature of 140 C. through an annular ring die having an overall diameter of /2 inch and an annulus .width of 0.04 inchat a flow rate of pounds per hour,

while maintaining a slightexcess air pressure inside the tube to support it, The product is a tube of foamed polystyrene having an outer diameter of about 2 inches, an inner diameter of about 1 inch, and an overall average density of 2 pounds per cubic foot.

When tested for flame-retardant properties by British Standard 3932, the product has a Flame Test Rating of 6 out of 6 self-extinguishing.

The flame-retardant agents of the invention are bis(arhalo-ar-alkenyloxyphenyl) compounds wherein the aromatic rings are linked by a covalent bond, a sulfur or oxygen atom, a secondary or tertiary amino group, or a divalent aliphatic group. When the aromatic rings are linked by a tertiary amino group, the third valency of the nitrogen atom can be satisfied by any suitable organic group, particularly, e.g., an alkyl group or a substituted alkyl group containing up to five carbon atoms. Preferably, the aromatic rings are linked-by a divalent aliphatic group, which can be straight-chained or branched,

saturated or unsaturated, and hydrocarbon or substituted hydrocarbon in nature, but which is most preferably an ,alkylidene' group. Particularly preferred are alkylidene groups containing up to 5 carbon atoms, e.g., methylidene and propylidene groups, although higher allkylidene groups can also be used if desired. When the divalent aliphatic group is a substituted hydrocarbon group, it

can containin addition to carbon and hydrogen-atoms.

such as halogen, oxygen or sulfur (e.g., in ether, ketone,

aldehyde, acid, or ester groups or their sulfur analogues), or nitrogen (e.g., in amine, amide, or nitrile groups).

Preferably, the halogen atom and the alkenyloxy group substituted on each aromatic ring are ortho or para (preferably ortho) to each other. It is also preferred to have two or more halo substitutents on each aromatic ring and to have each alkenyloxy group ortho or para to more than one halogen atom. In general, the halogen atoms, which can be the same or different, can be e.g., chlorine or bromine, although bromine is normally the preferred halogen because of the greater efliciency of bromo compounds as flame-retardant agents. The alkenyloxy groups in the molecule can be similar or different, and there can be more than one alkenyloxy group substituted on each aromatic ring. They preferably contain not more than 5, usually 3 or 4, carbon atoms, and the double bond is preferably in the 2,3-position relative to the oxygen atom. Allyloxy, methallyloxy, and crotyloxy groups are preferred, In addition to the alkenyloxy and halo substitutents, the aromatic rings can also bear substituents such as alkyl or alkoxy groups, e.g., methyl, ethyl, propyl, butyl, methoxy, ethoxy, etc.

Exemplary of the novel compounds of the invention are As mentioned above, the novel'compounds of the invention can be prepared by reacting an alkenyl halide with the appropriate bis(ar-halo-ar-hydroxyphenyl) compound wherein the aromatic rings are linked by a covalent bond, a sulfur or oxygen atom, a secondary or tertiary amino group, or a divalent aliphatic group, or

with a salt of such a compound. The alkenyl halide is preferably an iodide, but a mixture of an alkenyl bromide and sodium iodide can be used with good results. Preferably, the reaction is conducted in'a solvent such as an alcohol, e.g., methanol, ethanol, isopropanol, etc., or a ketone, e.g., acetone, methyl ethyl ketone, etc. When the reaction is with a salt, this is preferably a salt of an alkali metal, particularly sodium or potassium. Hydro gen halide formed in the reaction of a hydroxy-aromatic compound can be removed, e.g., by distillation or by reaction with a suitable acid acceptor such as an alkali metal carbonate. The reaction mixture can be heated andstirred if necessary. Suitable reaction temperatures are often in the range of 0150 C., particularly 55-l05 C.,

retardant agent in the lower part of the above range is usually suflicient, e.g., (ll-1.5%, especially 0.251%, particularly about 0.5%, of flame-retardant agent, based on the weight of the resin, can give tardant properties.

The resins which can be rendered flame-retardant in accordance with the invention include any normally flammable synthetic resins which can advantageously be given a degree of lflame-retardancy. In a preferred embodiment of the invention, the resin is a polymer of one or more excellent flame-reethylenically-unsaturated monomers, e.g., a hydrocarbon monomer such as ethylene, propylene, butylene, styrene, alpha-methylstyrene, 0-, m-, or p-methylstyrene, other aralkylstyrenes, etc., or other suitable monomers such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, the corresponding alkyl methacrylates, vinyl acetate and other vinyl esters, etc. Such polymers include interpolymers of one or more of the above monomers with minor amounts, e.g., up to about 20% by weight, of other monomers such as acrylonitrile, butadiene, isoprene, etc., as well as mixtures of two or more of such polymers. The invention is particularly applicable to polystyrene resins, such as polystyrene itself or a toughened polystyrene, i.e., a polystyrene having physically or chemically combined therewith a minor proportion, e.g., 1-15 by weight, of a natural or synthetic rubber, e.g., substantially linear or branched polymers of conjugated dienes, such as butadiene, isoprene, etc., including copolymers thereof with lesser amounts of comonomers such as styrene, acrylonitrile, methyl methacrylate, etc.

As indicated above, the invention is of particular value in providing foamable synthetic resins which can be expanded by conventional techniques to form foamed resins having an excellent degree of fiame-retardancy as well as good mechanical properties. As is well known, a foamable resin material contains a minor proportion of a blowing agent, which in general is a substance which volatilizes on heating, such as a low boiling liquid, or a chemical blowing agent. In some instances a volatile agent is one that is in the form of a vapor at atmospheric pressure and ordinary temperatures, such as 20 C., but it is preferably a volatile liquid, normally one that swells but does not dissolve the polymer. Exemplary of volatile substances that can be used are lower aliphatic hydrocarbons, e.g., a butane, a pentane, a hexane, cyclopentane, cyclohexane, etc.; lower alkyl halides such as methyl chloride, trichloromethane, 1,2-dichlorotetrafluomethane; and mixtures of these substances. The lower aliphatic hydrocarbons, especially the pentanes, are preferred, and in practice a petroleum fraction consisting predominantly of pentanes can be usefully employed. The blowing agent can also be a chemical blowing agent, e.g., a bicarbonate such as sodium bicarbonate or ammonium bicarbonate or an organic compound which yields nitrogen on heating such as dinitrosopentamethylenediamine or barium azodicarboxylate. The blowing agent is usually employed in a proportion of about 2-15%, especially 310%, based on the weight of the foamable material; for example, the use of about 6% by weight of a pentane fraction in conjunction with polystyrene gives excellent results. The foamable materials frequently contain additives such as nucleating agents, e.g., finely-divided silica, which regulate the cell size.

The flame-retardant agent can be added to the synthetic resin in any convenient way, e.g., by mixing in a mill or an extruder or by applying the flame-retardant agent to the surface of a shaped resin article, but a method that often presents practical advantages is to coat particles of the resin, especially foamable particles, with a thin surface layer comprising the flame-retardant agent. This can be accomplished by employing the flame-retardant agent in powder form or in conjunction with a solvent or liquid dispersion medium. In many instances an adhesive is preferably used, e.g., an oil such as a suitable mineral oil; a wax; or an ester, particularly a solid ester, such as a glyceride, for instance a monoor diacetate, or an ester of a long chain fatty acid, particularly a mono-ester. Thus there can be employed, e.g., an ester of lauric, stearic, palmitic, or oleic acid. Particularly good results are obtained using a monoester of sorbitan, especially the mono-laurate, mono-palmitate, or mono-stearate, or sorbitan trioleate. When the flameretardant agent is used in a liquid composition such as a solution or dispersion (which may or may not contain an adhesive), the composition can be aqueous or nonaqueous and can be applied, e.g., by spraying, rolling, or brushing. Moreover, if an adhesive is used, the adhesive can be applied first, for instance as a fairly mobile solution (e.g., a solution having a viscosity of less than 500 centipoises at 25 C.) in a solvent, and then the finely-divided flame-retardant agent can be dusted on by any suitable technique, e.g., tumbling the components together in a drum. Suitable solvents include alcohols such as methanol, ethanol, isopropanol, etc., and, when the resin particles are to be foamable, volatile liquids such as those mentioned above as being suitable blowing agents, e.g., a pentane or hexane. After the treatment, any residual solvent can be allowed to evaporate, if desired in a current of air.

The flame-retardant agents are also particularly useful in foamed resin materials produced by extrusion of a foamable resin composition comprising a blowing agent. In a preferred extrusion process, a volatile blowing agent such as a butane or a pentane is injected into the barrel of the extruder so that it is mixed with the resin to produce the foamable composition. The flame-retardant agent can be supplied in admixture with or incorporated in particles of resin fed to the extruder, or it can be dissolved in the blowing agent which is to be injected into the polymer in the barrel of the extruder. Alternatively, a premixed composition comprising the resin, the blowing agent, and the flame-retardant agent can be fed to the extruder. It is often convenient to use a particulate polymer the particles of which have been coated with the flame-retardant agent.

As an alternative to physical mixing, the flame-retardant agent can be incorporated in the resin during its production by the polymerizationof an ethylenically-unsaturated monomer. When this method of incorporation is employed, the polymerization conditions are those conventionally used for the polymerization of the monmer. Thus, the polymerization can be conducted by a mass, solution, emulsion, or suspension technique (preferably by a suspension polymerization technique), thermally or in the presence of a catalyst such as an azo compound, e.g., azobisisobutyronitrile, or a peroxy compound, e.g., cumene hydroperoxide, benzoyl peroxide, acetyl benzoyl peroxide, di-tbutyl peroxide, etc., alone or in conjunction with a reducing agent providing a redox system. Conventional reaction temperatures, e.g., 50200 C., and pressures, e.g., 1l0 atmospheres, can be used, and additives such as blowing agents, etc., can be present. When a suspension polymerization technique is employed, the aqueous system is agitated sufficiently to maintain suspension, and conventional suspending agents, e.g., water-insoluble inorganic oxides, hydroxides, and salts, and organic water-soluble polymers such as polyvinyl alcohols, methyl cellulose, gelatine, polyvinylpyrrolidone, carboxymethylcellulose and its watersoluble salts, and polyacrylic acids and their Water-soluble salts, can be employed. After the suspension polymerization, the polymer beads can be recovered by the usual techniques of allowing the reaction mixture to cool to ambient temperature, adjusting the pressure to atmospheric pressure, filtering off the beads, washing the beads if necessary, and drying them.

Foaming and molding operations performed on foamable synthetic resin compositions containing the flameretardant agents of the invention can follow ordinary practice. Thus, for example, the foamable particles can be heated by steam, hot water, or hot air, or under the influence of an infra-red heater, to produce prefoamed beads, which are preferably conditioned by exposing them to the atmosphere for a day or two before they are used in the molding operation. A suitable mold can then be partially or fully filled with the prefoamed beads and closed, and steam is injected through inlets in the mold walls. When foaming is complete, the steam supply is shut off, and the resulting flame-retardant product is allowed to cool before the mold is opened. Other methods of molding can also be employed.

It is obvious that many variations can be made in the products and processes set forth above without departing from the spirit and scope of this invention.

What is claimed is:

1. A foamable composition comprising a normally flammable polymer of an ethylenically-unsaturated monomer, a blowing agent, and, as a flame-retardant agent 2,2-bis (4- ally1oxy-3,S-dibrornophenyl) propane.

2. The composition of claim 1 wherein the polymer is a styrene polymer.

3. The composition of claim 2 wherein the styrene polymer is polystyrene.

4. In a process for extruding a normally flammable foamable synthetic resin composition containing a volatile blowing agent, the improvement which comprises incorporating into the foamable composition 2,2-bis(4-allyloxy- 3,5-dibromophenyl)propane.

8/1966 Eichhorn 260-2.5 FP

9/1966 Eichhorn 2602.5 FP

MURRAY TILLMAN, Primary Examiner M. F OELAK, Assistant Examiner U.S. Cl. X.R.

2602.5 B, 2.5 E, 4 AR, 28.5 R, 45.7 R, 570.6, 892, 893 

